Embodiments of the present invention relate generally to methods for separating workpieces such as sheets of glass, wafers, substrates, etc.
Hard optical materials including thin glass substrates, whether chemically-strengthened, thermally-strengthened or unstrengthened, have found wide-spread application in consumer electronics and other industries. For example, chemically- and thermally-strengthened glass substrates have been used as cover substrates for LCD and LED displays and touch applications incorporated in mobile telephones, display devices such as televisions and computer monitors, and various other electronic devices. To reduce costs associated with manufacturing such consumer electronics devices, large or common substrates are transported from the hard optical materials manufacturer to the materials user and then the user singulates the individual substrates from the common substrate using a device such as a mechanical scoring wheel or a laser.
Singulating individual glass substrates from a common glass substrate, however, can be difficult, especially when the common glass substrate is formed of chemically or thermally strengthened glass. For example, the magnitude of compressive stress and the elastic energy stored within the central tension region may make cutting and finishing of chemically or thermally strengthened glass difficult. The high surface compression and deep compression layers make it difficult to mechanically scribe the glass substrate as in traditional scribe-and-bend processes. Furthermore, if the stored elastic energy in the central tension region is sufficiently high, the glass may break in an explosive manner when the surface compression layer is penetrated. In other instances, the release of the elastic energy may cause the break to deviate from a separation path. Similarly, there are difficulties with separating or singulating other hard optical materials adaptable for use as cover materials for electronic displays such as corundum, ceramics, semiconductors, metal or metal alloys, and glass-ceramics. Accordingly, a need exists for reliable methods for separating hard optical material including strengthened glass substrates.